Reduced erbium-doped ceria nanoparticles: one nano-host applicable for simultaneous optical down- and up-conversions

This paper introduces a new synthesis procedure to form erbium-doped ceria nanoparticles (EDC NPs) that can act as an optical medium for both up-conversion and down-conversion in the same time. This synthesis process results qualitatively in a high concentration of Ce(3+) ions required to obtain high fluorescence efficiency in the down-conversion process. Simultaneously, the synthesized nanoparticles contain the molecular energy levels of erbium that are required for up-conversion. Therefore, the synthesized EDC NPs can emit visible light when excited with either UV or IR photons. This opens new opportunities for applications where emission of light via both up- and down-conversions from a single nanomaterial is desired such as solar cells and bio-imaging

An Environmentally Friendly Conductive Ink Made Using Transgenic Spider Silk Protein and Silver Salts

The goal of this study was to demonstrate that it is possible to formulate an electrically conductive, stretchable and environmentally friendly ink or coating. This is made possible by harnessing the properties of biomimetic spider silk obtained from transgenic goats. In this experiment we formulated four inks using spider silk, silver trifluoroacetate and carbon nanotubes (CNT). We utilized Polyethylene terephthalate (PET), spider silk, natural rubber (Latex) and polystyrene-block-isobutylene-block-styrene(SIS) as substrates to demonstrate the flexible nature of the ink/coating. We then conducted surface characterization using FTIR and SEM to verify the presence of our coating and quantified the thickness of our coatings. We measured the conductivity of the ink using an Ohm meter. Our preliminary results indicate successful formulation of an ink that meets the parameters described above. Inks formulated using spider silk and AgTFA are in fact more stable and conductive than other inks tested in this experiment. We also found little or no success with the other three inks described in the experiment. This study serves as a proof of concept and starting point for optimization of such inks for use in the bio medical and technology sectors

Conductive Ink Meets Spider Silk

Spider silk proteins can be created synthetically and are highly valued for their strength, durability, and flexibility. By altering the genome of goats, silk worms, and the bacteria E. coli we are able to manufacture spider silk products in lab. The production and manipulation of these ‘recombinant spider silk proteins’ along with the process of aqueous solubilization can yield many useful spider silk materials such as films, fibers, gels, coatings, and more. Conductive ink is a recent and popular scientific discovery that let’s you create flexible working circuits. This product has many applications including RFID tags, circuit boards, and printers. However, most conductive inks contain a highly toxic organic compound known as butanone along with a conductive salt. Our research is to prove that replacing butanone with spider silk proteins in conductive inks will still create a flexible and durable circuit without the toxicity. This non-toxic conductive ink could prove useful when applying the circuit directly into living systems. We also think that using spider silk proteins in our circuits will improve the durability and elasticity of the circuits created

Piezoresponse, mechanical, and electrical characteristics of synthetic spider silk nanofibers

This work presents electrospun nanofibers from synthetic spider silk protein, and their application as both a mechanical vibration and humidity sensor. Spider silk solution was synthesized from minor ampullate silk protein (MaSp) and then electrospun into nanofibers with a mean diameter of less than 100 nm. Then, mechanical vibrations were detected through piezoelectric characteristics analysis using a piezo force microscope and a dynamic mechanical analyzer with a voltage probe. The piezoelectric coefficient (d33) was determined to be 3.62 pC/N. During humidity sensing, both mechanical and electric resistance properties of spider silk nanofibers were evaluated at varying high-level humidity, beyond a relative humidity of 70%. The mechanical characterizations of the nanofibers show promising results, with Young’s modulus and maximum strain of up to 4.32 MPa and 40.90%, respectively. One more interesting feature is the electric resistivity of the spider silk nanofibers, which were observed to be decaying with humidity over time, showing a cyclic effect in both the absence and presence of humidity due to the cyclic shrinkage/expansion of the protein chains. The synthesized nanocomposite can be useful for further biomedical applications, such as nerve cell regrowth and drug delivery. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.NPRP from the Qatar National Research Fund (Qatar Foundation) [NPRP 7-1724-3-438

Piezoresponse, Mechanical, and Electrical Characteristics of Synthetic Spider Silk Nanofibers

This work presents electrospun nanofibers from synthetic spider silk protein, and their application as both a mechanical vibration and humidity sensor. Spider silk solution was synthesized from minor ampullate silk protein (MaSp) and then electrospun into nanofibers with a mean diameter of less than 100 nm. Then, mechanical vibrations were detected through piezoelectric characteristics analysis using a piezo force microscope and a dynamic mechanical analyzer with a voltage probe. The piezoelectric coefficient (d33) was determined to be 3.62 pC/N. During humidity sensing, both mechanical and electric resistance properties of spider silk nanofibers were evaluated at varying high-level humidity, beyond a relative humidity of 70%. The mechanical characterizations of the nanofibers show promising results, with Young’s modulus and maximum strain of up to 4.32 MPa and 40.90%, respectively. One more interesting feature is the electric resistivity of the spider silk nanofibers, which were observed to be decaying with humidity over time, showing a cyclic effect in both the absence and presence of humidity due to the cyclic shrinkage/expansion of the protein chains. The synthesized nanocomposite can be useful for further biomedical applications, such as nerve cell regrowth and drug delivery

Melt electrospinning of thermoplastic polymers

This dissertation is concerned about developing of melt electrospinning strategies of thermoplastic polymers. The goal was to generate polypropylene nanofibers from the polymer melt instead from the polymer solution. Through this method, organic, toxic or environmentally non-friendly solvents can be avoided offering a clean process for nanofibers production. Melt electrospinning necessitates the use of polymer melts with lower melt viscosity since high melt viscosities inhibit the formation of ultrafine fibers. The generation of ultra-fine polypropylene nanofibers to utilize these fibers in filter media was studied. The ultra-fine size fibers below 1 µm offer great surface area that assists us to be used as filter media. At the beginning, a simple melt electrospinning device was designed and the melt viscosity of polypropylene was influenced. The effect of the melt viscosity on the produced fiber diameter was studied. Furthermore, the effects of the ambient and the processing parameters on the electrospinning process and the resulting fiber diameter were studied. In the next chapter, the melt viscosity of polypropylene was influenced by blending of different molecular weights polypropylenes, by addition of small molecules (sodium stearate) and by increasing of the melt temperature. The aim is to recognize the melt viscosity limits which enable us to obtain ultra-fine polypropylene fibers. In the following chapter, process and ambient parameters and their effect on fiber diameter were studied. These parameters were investigated in order to optimize the conditions for generation of small fibers. Furthermore and after investigation of the effect of melt viscosity and processing parameters, the chosen polypropylene mixtures were mixed with nucleating. Three different types of nucleating agents were used to enhance the nucleation process in polypropylene electrospun fibers. The amounts of nucleating agents were altered in order to obtain the highest possible melt enthalpy (dH) that indicates the highest degree of crystallization. The effects of nucleating agents’ type and their amount on the fiber diameters and the degree of crystallization were studied

Electrospinning

Our research is centered on creating synthetic fibers with our spider silk proteins (MaSp1/MaSp2) incorporated into them. This is done through two processes; Electrospinning and Wet Spinning. A liquid dope is created using our two proteins and different solvents. The first process for creating synthetic fibers is using our electrospinning instrument, in which our dope is placed into a syringe and a positive electrode is attached to it while the target (rotating spindle or stationary target) has the negative electrode attached. The flow rate, spindle rotation, and current (approximately 28 kV) can vary depending on the desired situation. Once all three parameters have been chosen, the voltage ejects the dope at an incredibly quick rate inducing nanofiber formation on the spindle, which can then be collected and rolled into tough fibers. The second method is that of wet spinning, in which the dope is ejected into a solution of either water, IPA, or methanol. As the fiber forms within the liquid it is then taken and placed onto Godets, a system which allows for different rates of stretch within different solvent baths. Both techniques are used to combine our 2 proteins with different fibers such as nylon, with the potential to increase the fibers mechanical properties

Improved Electrical Conductivity of Carbon/Polyvinyl Alcohol Electrospun Nanofibers

Carbon nanofibers (CNFs) gained much interest in the last few years due to their promising electrical, chemical, and mechanical characteristics. This paper investigates a new nanocomposite composed of carbon nanofibers hosted by PVA and both are integrated in one electrospun nanofibers web. This technique shows a simple and cheap way to offer a host for CNFs using traditional deposition techniques. The results show that electrical conductivity of the formed nanofibers has been improved up to 1.63 × 10-4 S/cm for CNFs of weight 2%. The peak temperature of mass loss through TGA measurements has been reduced by 2.3%. SEM images show the homogeneity of the formed PVA and carbon nanofibers in one web, with stretched CNFs after the electrospinning process. The formed nanocomposite can be used in wide variety of applications including nanoelectronics and gas adsorption. © 2015 Nader Shehata et al

Resistive behaviors of spider silk nanofibers in humidity controlled environments

Spider silk is becoming more useful for its desired properties as more information about the nanostructure is discovered. Due to the fact that this protein is nearly impossible to mass produce directly from the spider, the protein coding gene has been duplicated from the spider genome and inserted into the E. coli, goat, alfalfa, and silkworm genomes. This has allowed us to extract the produced protein from the transgenic hosts at a larger scale than the spiders offer. Spider silk is one of the strongest and most elastic fibers found in nature and these two characteristics, along with others others, have very promising applications in many different areas. Areas including biomedical, automobile, military, and sports equipment all have products that could be benefitted by this spider silk. Considering the biomedical realm, there are encouraging results in the mechanical and chemical properties of the spider silk protein for tendon and ligament repair, tissue scaffolding, and also neural system regeneration. The aim of this project is to take the spider silk protein (M4) produced from the transgenic goat and spin it into nanofibers via electrospinning technique and analyze the properties of this fiber. Specifically, we will use FTIR (Fourier Transfer Infra Red) Spectroscopy, SEM (Scanning electro microscope) analysis, mechanical property analysis, as well as resistance testing at variable relative humidity levels (RH) to record the resistive behavior of the fiber as if it were in an actual neural system